Refrigerating system



Oct. 25, 1932. y B. c. SHIPMAN 1,885,017

REFRIGERATING SYSTEM Filed July 22, 1927 Patented Oct. 25, 1932 PATENT OFFICE BENNET CARROLL SHIPMAN, OF SAN MATEO, CALIFORNIA BEFRIGERATING SYSTEM Application filed July 22, 1927. Serial No. 207,745

My invention relates to that type of refrigcratingv systems utilizing the condensation and evaporation of a volatile fluid. Its objects are first, to increase the efficiency of such systems, and second, to reduce the cost of installation, especially where relatively long suction lines are required, by eliminating the necessity for insulating such lines.

Fig. 1 is a diagrammatic sketch of a refrigcrating system to which my invention is applied. 1 is a suitable compressor driven by any source of power not shown; 2 is a suitable condenser; 3 is a liquid supply line feeding one or more evaporators through branch 5 lines, 3411.; 4 is a heat interchanger adapted to pass incoming liquid through one of its elements and outgoing gas through the other of its elements; 5 is a liquid admission valve, here shown as a float valve, but may be in non-flooded systems a reducing or expansion valve; 6 are evaporators, here sho n as flooded, and having depending tubes, 6a, to increase the effective cooling surface; 7a are branch return lines from the evaporators to a common suction line, 7 8 is a saturator supplied with liquid refrlgerant through an admission valve, 9, here shown as a float valve; and 10 is the return gas line to the compressor.

The operation of the system is as follows:

' An adequate supply of refrigerant compressed y the compressor, 1, and liquefied y the condenser, 2, flows under such condensing pressure through the lines, 3 and 3a,

' and through one element of the heat interchangers, i, to the liquid admission valves, 5,

until the evaporators, 6, are supplied with a predetermined amount of refrigerant. lhe

gas resulting from the evaporation of such refrigerant passes out through the other element of the heat interchanger, 4:, thence through lines, 7a and 7, to the saturator, 8.

The saturator, 8, may be, as shown, merely a vessel containing a suitable quantity of. liquid control valve 9, from the main liquid supply line, 3, and-the returning1 gas may be delivered, as shown, under t e surface of such liquid through aperforated pipe for better 59 contact with the liquid, the purpose being to refrigerant replenished through the liquid insure complete cooling of the returning gas to the saturation temperature corresponding to the suction pressure. Other arrangements could just as well be used.

From the above description it is evident that the gas leaving the evaporators substantially at the temperature of the liquid in the evaporators will, by means of theheat interchangers, reduce the temperature of the incoming liquid and itself become superheated substantially to the initial temperature of the incoming liquid,in most cases that of the surrounding atmosphere. In passing thence back to the compressor this gas therefore, can not receive any additional heat, and hence no insulation on the suction line is required to prevent loss or the "formation of frost or sweat. However, if the gas be taken into the compressor in this superheated condition, a loss of power and capacity will result due to the lesser density of the gas for a given pressure. To restore the gas to the initial density it had on leaving the evaporators, the saturator, 8, is provided to reduce the temperature of the returning gas to that corresponding to its pressure, and thereby secure the maximum efliciency from the compressor. The gas, therefore, enters the compressor at its maximum density for the pressure involved, and the result thermodynamically is in effect the same as if the compressor were attached im mediately at the outlets of the evaporators without any suction line intervening. An arrangement of the liquid supply line in close contact with, or within the suction line would also serve the purposeof a heat interchanger.

A specific case will indicate the results'to be secured by the above arrangement. Assume the following conditions as fairly representative: atmospheric temperature 86 F, condensing temperature 86 F, evaporating temperature 20 F, and sulphur dioxide as the refrigerant. Under these conditions the characteristics of this refrigerant are as follows: total heat of saturate S0 at 20 F, including both heat of the liquid above 40 F.

and the heat of vaporization, is 184.52 B. t. u.

per pound; the pressure corresponding to 20 F. is 1? .18 lbs. per square inch absolute; the total heat of the gas at 17.18 lbs. per square inch superheated to 86 F. is 196.0 B. t. u. per pound; the heat of vaporization at 20 F. is 165.32 B. t. 11. per pound; the heat of the liquid at 20 F. is 19.2 B. t. u. per pound. Hence to heat the gas at 17.18 lbs. per square inch from 20 F. to 86 F. requires the difference between 196.0 and 184.52 B. t. u. per pound, or 11.48 B. t. u. per pound. The heat of the liquid above-40 F. at 86 F. is 42.12 B. t. u. per pound. Therefore the heat re mai'ning in the liquid after removing that required to heat the gas from 20 F. to 86 F. is the difference between 42.12 and 11.48 or 30.64 B. t. u. per pound and the resulting temperature of the liquid will be 53 F. at which it will be admitted to the evaporators.

The usual refrigeratin effect of one pound of SO under the conditions of 20 F. evaporation and 86 F. condensation, or atmos-.

pheric temperature, without any heat interchange is the heat of vaporization at 20 F., or 165.32 B. t. u. per pound less the heat of the liquid between the temperature at admission, 42.12 B. t. 11. per pound, and the temperature after admission, 19.2 B. t. u. er pound, namelv 22.92 B. t. u. per pound, which amount must be abstracted by evaporation of itself to cool itself, thus leaving the difference (16532-2292) 142.40 B. t. u. per pound available for extraneous refrigerating effect. On the other hand when sub-cooling the liquid by means of the resulting exiting gas, the refr1gerating effect of one pound of 0 under the same conditions of 20 F. evaporation and 86 F. condensation is the heat of vaporization at 20 F., namely 165.32 B. t. u. per pound less the heat of the liquid between the temperature at admission, 30.64 B. t. u. per pound, and the temperature after admis sion, 19.2 B. t. u. per pound, namely 11.44 B. t. u. per pound instead of 22.92 B. t. u.

er pound, which. amount must be abstracted y evaporation of itself to cool itself, thus leaving the difference (165.3211.44) 153.88 B. t. u. per pound available for extraneous refrigerating efi'ect instead of only 142.4 B. t. u. per pound as is usual. Or conversely only 0.925 pound of refrigeEnt isrequired to produce the same refrigerating effect.

The volume of S0 gas at 17.18 lbs. per square inch absolute and 20 F. is 3.951 cubic feet per pound, and the volume at 17.18 lbs. per square inch and 86 F. is 5.386 cubic feet per pound. As above set forth, it requires 11.48 B. t. u. to heat one pound of S0 gas from 20 F. to 86 F., hence it also requires the absorption of the same amount of heat to cool the same gas the same number of degrees. It therefore requires in the saturator the evaporation ofpounds (.08061 lbs.)

ing as a standard the refrigerating effect produced by one pound of SO without subcooling and re-saturation, namely 142.4 B. t. u. per pound, the resulting gas in the evaporator is 3.951 cubic feet at 20 F. and 17.18 lbs. per square inch and 5.386 cubic feet at 86 and the same pressure, to which point it will superheat on its way back to the compressor if even only a relatively small distance. By the sub-cooling above described only 0.925 pounds of refrigerant is required and the resultin gas is 3.655 cubic feet at 20 F. and 17.181 s. per square inch'pressure and 4.982 cubic feet at the same pressure when it is superheated to 86 F. in the heat interchanger. Nevertheless it is again reduced to the original volume, 3.655 cubic feet, in the saturator. To this however is added the gas formed from the liquid in the saturator required both to cool itself and to cool the arriving superheated gas. As shown above this amounts to 0.08061 pounds representing a volume of 0.3185 cubic feet thus making a total volume of 3.9735 cubic feet to be handled by the compressor against a volume of 5.386 cubic feet necessary in the usual case, in order to produce the same amount of refrigeration. In other words but 73.8-per cent of the capacity and power are required. Hotter conditions well within the range of normal operating conditionsin summer will show greater saving.

It is evident that various devices could be used for admission valves, heat interchangers and saturators. I do not claim any such devices of themselves as such, or any specific construction, but the combination of them substantially as shown and described to produce more efficient results and more economical installation, as follows:

I claim:

1. In a refrigerating system including a compressor, condenser, evaporator, liquid refrigerant supply and gas suction lines, the said supply and suction lines connected in mutual heat exchange relationship and a refrigerant gas saturator in the gas suction line adjacent to the compressor.

2. Ina refrigerating system including means for liquefying a refrigerant, main and branch liquid refrigerant supply lines, main and branch gas refrigerant suction lines, and a pluralit of evaporators connected in multiple to said lines, the said branch supply and suction lines for each evaporator connected in mutual heat exchange relationship, and a gas refrigerant saturator in the main suction line adjacent to the said liquefying means 3. In a refrigerating system including means for liquefying a refrigerant, main and branch liquid refrigerant supply lines, main and branch gas refrigerant return lines, a plurality of evaporators connected in multiple to said lines, and liquid admission control valves to said evaporators, the combina-' tion therewith of double chambered heat interchangers adjacent to their respective eva orators, one chamber of which is connected in the liquid supplly branch line and the other chamber of w ich is connected in the gas return branch line of each of the said evaporators, and a vessel connected to the main gas return line adjacent to the liquefying means connected by means of a liquid refrigerant control valve to the said main liquid refrigerant supply line.

4. In a refrigerating system, the combination of means for compressing and condensing a refrigerant, means for evaporating said refrigerant, means for conveying the liquid refrigerant to and the vaporized refrigerant from the said evaporating means, means adjacent to said evaporating means for trans feiring heat from the liquid refrigerant before enterin the evaporating means to the vaporized re rigerant after leaving the evaporating means with means adjacent to the said compressing means adapted to absorb the super heat of the vaporized refrigerant before reaching the compressing means.

5. In a refrigerating system, the method of utilizing the evaporated refrigerant arising from the eva orator to sub-cool the incoming liquid re rigerant before admission' to the said evaporator and successively recooling the said evaporated refrigerant before admission to the compressor.

6. In a refrigerating system, the method of successively superheating the evaporated refrigerant arising from an evaporator by means of the incoming liquid refrigerant before admission to said evaporator and recooling the said superheated refrigerant gas adjacent to the compressor before admission to the same. a

7. In a refrigerating system, the method of sequentially cooling the incoming liquid refrigerant before admission to the evaporator by means of the vaporized refrigerant arising therefrom and of recooling the said vaporized refrigerant before admission to the compressor.

' BENNET CARROLL SHIPMAN. 

